I have hunted and lived in the San Luis valley of Colorado for years. In the last 15 years if someone from the government catch's you hunting arrowheads on state or Fed ground you will have big problems. They have all the state lands posted with signs. Your not allowed to pick up one arrowhead. You can be a few miles from the road and you will see the signs. You can dig or hunt on private lands and your ok. The problem is their are not any places left to hunt. The government has bought up some of the big ranch's and locked the gates. You know the government employees have personal access to the ranch. This was a old land grant had some of the best arrowhead hunting around but was private back then. I have a large collection and I will bury it before I ever leave to a government museum like a lot of people do. They will not get any information from me if I make a discovery on private land. It is not worth taking the risk to hunt on public lands. You never know who is watching. I knew someone who was walking down a sandy road and got stopped and accused of hunting arrow heads. Best advice don't have anything on you if you get stopped.
Thanks for all the responses.... we're off to southern Colorado for an arrowhead hunt; We found a private ranch which welcomed us...for $$ of course. Had dinner reservations next week at the Inn of Glen Haven, just outside of Estes Park. We don't believe it is still there. Our cabin just west of Estes Park is gone...hope everyone is safe!
Searched intensively on Google for "Colorado" and "arrowhead hunting". Eventually found a location for surface hunting. (Private Ranch which leased out camping spaces) They had large areas for isolated arrowhead hunting but was covered with lots of rocks. Made it difficult. Did not find any "digs".